Specifically, Dactyl was discovered in images from 28 August 1993 taken by the Galileo probe during its flyby. The images were transmitted back to Earth somewhat later, and the satellite was recognized 17 February 1994.

This image of Dactyl was taken by Galileo on 28 August 1993 from a range of 3900 km. Resolution is about 39 meters. The south pole is near the center of the unlit portion on the left. The largest crater, on the terminator (at 138°E, 39°S), is 280 meters across and has been named Acmon. A second 160-meter diameter crater at 220°E, 46°S (in shadow at lower center) is named Celmis. (Image credit: NASA/JPL)

Dactyl's orbit is poorly constrained by the available Galileo imagery. Rather, by assuming Dactyl to be in a bound orbit, constraints on Ida's mass have been found.

A shape model for Dactyl was obtained from Galileo imagery by Veverka et ali [V96a]; the maximum topographic variation from the best fit ellipsoid is 0.13 km. No evidence of rotation of Dactyl was obtained. Together with the fact that Dactyl's long axis is oriented towards Ida, this is consistent with Dactyl being in synchronous rotation with respect to Ida. Dactyl appears to be, in general, similar in composition to Ida; some slight differences, including a higher pyroxene/olivine ratio, are suggested [V96a].